Purifying aluminous materials.



duction of all of the oxidsof ,plete'.

lln a prior" Patent No. 960,712, patentedhill nnwrs'n. sermons, on NIAGARA FALLS, new roux, assrcn'on T0 NORTON COMPANY,

OE WORCESTER, MASSACHUSETTS, A CORPORATION OF MASSACHUSETTS.

rum Erma anmumous marnniats.

neeaaea.

No Drawing.-

To allwhom it may concern .1

Be it known that I, LEWIS E. a citizen of the United States, Niagara Falls,- and. State of New York, have invented'certain new and useful Improvements in Purifying Aluminous Materials, of which the SAUNDERS, res1d1ng at following is a specification.

The object of this invention is to provlde a method whereby crystalline alumina of relatively high purity may be prepared in the electric. furnace from such impure raw materials as calcined bauxite and the like.

It is known that a partial reduction of .the' non-aluminous oxids normally present in bauxite may be brought about by incorporating with the charge to be fused a small proportion of carbon. If, however, the proportion of carbon be increased to about the amount theoreticallynecessary for the reiron, silicon and titanium, it is found that a highly objectionable reduction of alumina occurs. It is customary therefore to use carbon in decidedly less proportion than would be required for a. complete reduction of the-oxid impurities, with the result that the purification attained ishighly incom- June 7,1910, I have pointed out that this dificulty may befavoided by performing the operation in two stages, in the first of -w ich a substantially complete reduction of the impurities together' with a partial reduction; of alumina,

is accomplished,

.while in the second operating stage, pertill.

. solid oxidizing formed after the ,removalof the reduced impurities, the reduction products of alumina are. re-oxidized to alumina, for example, by means of air or other oxidizing gas. In a copending application, Serial No. 186,921, filed Aug. 18, 1917, l have further pointed out that. this re-oxidation may be ad.- vantageously performedby means of certain agents, including bauxite.

According to the present invention, a somewhat slmilar result istaccomplished in a single stage by introducing into the charge a'relatively' large proportion, usually ten to-twenty per cent. by weight, oreven more,

of metallic iron. I have di "covered that in procined to or presence 0t metallic iron in suficienfi ortions', it is possibleto add to the ca auxite. proportions of carbon up Specification of Letters Patent. Application filed August It, 1917. Serial No.

in the county of Niagara CO tion required for the I of course known partial andmay be obtained by Patented June ill, 193%.

even somewhat exceeding those theoretically necessary for the reduction of the total quantity of non-aluminous oxids (assuming as the gaseous reaction product) without appreciable or objectionable reduction of alumina. In practice I prefer to use the carbon in about the theoretical proporreduction of the nonaluminous oxids. The proportion of iron used increases with increasing percentages ;of impurltles 1n the bauxite or other aluminous raw material, and is therefore,

broadly speaking, proportionate to the amount of the carbon addition; although the practice of the method permits of considerable varia tions in this respect.

lhe manner in which metallic iron serves to carbon is not certainly ascertained. llt is that molten iron is an ex cellent solvent for carbon, and sumed' that carbon in solution in iron or combined therewith ing alumina under the conditions existing in the furnace. Also, since molten iron is likewise a solvent for silicon and titanium it is probable that its presence serves, by withdrawingv the reduced metals from the field of reaction, to disturb the equilibrium represented by such reversible reactions asfWhatever the explanation may be, if have process in the manufacture of aluminous" abrasives yields a product-having a charac teristic. fine grain. The use of metallic iron in this process presents the, great economical advantage over a similar use of iron oxid, together with the added proportion of carbon needed for its reduction, that electrical energy is not con sumed in a reducing operation which may be carried out at less cost in an ordinary metallurgical furnace. Aside from this consideration of cost, quite similar results as regards purity and character of product adding to the calcined bauxite to be fused, in addition to. the

protect the alumina from reduction by.

it may be asis incapable of reduc-' amount of carbonrequired for reducing the impurities therein, an added amount of ron oxid equivalent say to ten to twenty per cent. by weight of metallic iron, together with the further quantity of carbon necessary for the reduction of this added iron oxid, or the greater portion thereof.

1. The hereindescribed process of purifying aluminous materials and producing crystalline alumina, whlchconsists in fusing the impure aluminous charge with a proportion of carbon approximating that theoretically required for complete. reduction of the non-aluminous oxids, in presence of metallic iron in suflicient proportion to prevent material reduction of alumina.

2. The hereindescribed process of purifying aluminous materials and producing crystalline alumina, which consists in fusing the impure aluminous charge with a proportion of carbon approximating that theoretically required for complete reduction of the non-aluminous oxids, in presence of upward of tenpercent-by weight of metallic iron. I 1 I In testimony whereof I aifix my signature.

' J LES SAUNDERS. 

